Yes, no doubt Davis is going to be a complete monster ... but he may not even be as NBA ready as MKG.
Plus there's the fact that we currently have a budding all-star PF who spaces the floor, and a young Center coming over next year who should provide lots of defence, shot blocking, and much more in our lineup.

Our more glaring needs will be in scoring production and strong D from the wing.
Eventhough most people have MKG as a SF, he is only 6'7 ... no doubt he could guard SG's - they had him on Baylor's PG Jackson, because he was a scoring threat.